This disclosure relates generally to methods and systems for counterfeit prevention, and more particularly to a system and method for automatically embedding miniature security marks in documents or images.
Current counterfeit prevention systems are mainly based on the use of digital watermarks, a technique which permits the insertion of information (e.g., copyright notices, security codes, identification data, etc.) to digital image signals and documents. Such data can be in a group of bits describing information pertaining to the signal or to the author of the signal (e.g., name, place, etc.). Most common watermarking methods for images work in spatial or frequency domains, with various spatial and frequency domain techniques used for adding watermarks to and removing them from signals.
For spatial digital watermarking the simplest method involves flipping the lowest-order bit of chosen pixels in a gray scale or color image. This works well only if the image will not be subject to any human or noisy modification. A more robust watermark can be embedded in an image in the same way that a watermark is added to paper. Such techniques may superimpose a watermark symbol over an area of the picture and then add some fixed intensity value for the watermark to the varied pixel values of the image. The resulting watermark may be visible or invisible depending upon the value (large or small, respectively) of the watermark intensity.
Spatial watermarking can also be applied using color separation. In this approach, the watermark appears in only one of the color bands. This type of watermark is visibly subtle and difficult to detect under normal viewing conditions. However, when the colors of the image are separated for printing or xerography, the watermark appears immediately. This renders the document useless to the printer unless the watermark can be removed from the color band. This approach is used commercially for journalists to inspect digital pictures from a photo-stockhouse before buying un-watermarked versions.
There are several drawbacks to utilizing digital watermarking technology. To retrieve a watermark, extraction hardware and/or software is generally employed. Because a digital watermark usually has a fairly large footprint, detectors employed to read the digital watermarks often require significant buffering storage, which increases detection costs.
An alternate counterfeit prevention system, miniature security marks, may be utilized to remedy this problem. Miniature Security Marks (MSMs) are composed of small, virtually invisible marks that form certain configurations. The MSMs can be embedded in documents or images to be protected. When the documents or images are scanned, processed, and sent to a printer, the MSM detectors in the imaging system may recognize the embedded MSM marks and defeat the counterfeit attempts. The MSM has an advantage over existing technologies, such as watermarking, in that it requires only very simple and inexpensive detectors. Consequently, the MSM may be applied to many devices in a cost-effective manner.
Embedding MSMs in an image is a complicated process involving determination of the best mark locations and adjusting mark parameters. As usually multiple conflicting requirements such as higher detection rate and lower visibility exist, a try-and-error approach requires skill and experience. Additionally, it is labor intensive and usually does not yield optimal results. In order to remedy this problem as well as other problems, a system and method need to be developed to assist in the MSM embedding process.
All U.S. patents and published U.S. patent applications cited herein are fully incorporated by reference. The following patents or publications are noted:
U.S. Patent Application Publication No. 2006/0115110 to Rodriguez et al. (“Authenticating Identification and Security Documents”) describes a system for authenticating security documents in which a document includes a first surface having a first and second set of print structures and a second surface. The sets of print structures cooperate to obscure the location on the first surface of the second set of print structures. The second set of print structures is arranged on the first surface so to provide a reflection pattern, such as a diffraction grating. The second set of print structures is preferably provided with metallic ink on the first surface.
U.S. Pat. No. 6,694,042 to Seder et al. (“Methods for Determining Contents of Media”) enables a variety of document management functions by printing documents with machine readable indicia, such as steganographic digital watermarks or barcodes. The indicia can be added as part of the printing process (after document data has been output by an originating application program), such as by printer driver software, by a Postscript engine in a printer, etc. The indicia can encode data about the document, or can encode an identifier that references a database record containing such data. By showing the printed document to a computer device with a suitable optical input device, such as a webcam, an electronic version of the document can be recalled for editing, or other responsive action can be taken.
U.S. Pat. No. 7,002,704 to Fan (“Method and Apparatus for Implementing Anti-counterfeiting Measures in Personal Computer-based Digital Color Printers”) teaches a system for rendering an electronic image representation associated with a software application program. The system includes a PC-based host processor programmed to execute the software application program, a temporary storage device associated with the host processor, and a printer interfaced to the host processor. A printer driver routine is operative on the host processor and determines whether the electronic image representation is of a counterfeit document by examining at least a portion of the electronic image representation when stored in the temporary storage device during the course of printing the electronic image representation at the printer.
The disclosed embodiments provide examples of improved solutions to the problems noted in the above Background discussion and the art cited therein. There is shown in these examples an improved method for embedding miniature security marks within documents and images, utilizing a mark parameters database, graphical user interface, and detection simulator. The method includes predicting detection error rates for each pixel location of a host image, defined as a digital representation of at least one recipient of the miniature security marks. The detection error rates for each pixel are displayed with the host image on a graphical user interface and the desired miniature security mark locations are selected. At least one set of miniature security mark parameters is identified, with the parameters being mark parameters that enable determination of an optimized balance between detectability and visibility of the miniature security marks. The host image with the miniature security mark is displayed on the graphical user interface for review and adjustment by an operator.
In an alternate embodiment there is disclosed a system for embedding miniature security marks within documents and images, utilizing a mark parameters database, graphical user interface, and detection simulator. The system includes means for predicting detection error rates for each pixel location of a host image, defined as a digital representation of at least one recipient of the miniature security marks. The system provides means for detection of the error rates for each pixel. These are displayed with the host image on a graphical user interface and means are provided for selecting the desired miniature security mark locations. The system identifies at least one set of miniature security mark parameters, with the parameters being mark parameters that enable determination of an optimized balance between detectability and visibility of the miniature security marks. The host image with the miniature security mark is displayed on the graphical user interface for review and adjustment by an operator.
In yet another embodiment there is disclosed a computer-readable storage medium having computer readable program code embodied in the medium which, when the program code is executed by a computer, causes the computer to perform method steps for embedding miniature security marks within documents and images, utilizing a mark parameters database, graphical user interface, and detection simulator. The method includes predicting detection error rates for each pixel location of a host image, defined as a digital representation of at least one recipient of the miniature security marks. The detection error rates for each pixel are displayed with the host image on a graphical user interface and the desired miniature security mark locations are selected. At least one set of miniature security mark parameters is identified, with the parameters being mark parameters that enable determination of an optimized balance between detectability and visibility of the miniature security marks. The host image with the miniature security mark is displayed on the graphical user interface for review and adjustment by an operator.